Inspecting a multilayer sample

ABSTRACT

Inspecting a multilayer sample. In one example embodiment, a method may receiving, at a beam splitter, light and splitting the light into first and second portions; combining, at the beam splitter, the first portion of the light after being reflected from a multilayer sample and the second portion of the light after being reflected from a reflector; receiving, at a computer-controlled system for analyzing Fabry-Perot fringes, the combined light and spectrally analyzing the combined light to determine a value of a total power impinging a slit of the system for analyzing Fabry-Perot fringes; determining an optical path difference (OPD); recording an interferogram that plots the value versus the OPD for the OPD; performing the previous acts of the method one or more additional times with a different OPD; and using the interferogram for each of the different OPDs to determine the thicknesses and order of the layers of the multilayer sample.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.15/486,146, filed on Apr. 12, 2017, the disclosure of which isincorporated herein by reference in its entirety.

FIELD

The embodiments discussed in this disclosure relate to inspecting amultilayer sample.

BACKGROUND

During an automated manufacturing process, a multilayer sample ofmaterial, such as a multilayer wafer, may be inspected usingconventional inspection systems to determine the overall thickness ofthe multilayer sample and to determine thicknesses of the variouslayers. During the automated manufacturing process, while thecomposition of each of the layers is often known, the order of thelayers, and the corresponding orientation of the layers, is oftenunknown.

For example, during an automated manufacturing process, a multilayerwafer may have a silicon layer and a silicon dioxide layer, and themultilayer wafer may need to be oriented with the silicon layer on topto allow the silicon layer to be ground down during the automatedmanufacturing process to a specific thickness. Therefore, a conventionalinspection system may be positioned above the multilayer wafer toinspect the multilayer wafer as it travels through the automatedmanufacturing process in order to measure the thickness of the topsilicon layer to verify that the silicon layer is successfully grounddown to the specific thickness. In this example, however, the multilayerwafer may inadvertently become turned upside down during the automatedmanufacturing process such that the silicon layer, which should be onthe top to be exposed for grinding down, ends up on the bottom. Whilethe conventional inspection system may be able to determine that themultilayer wafer has a top layer and a bottom layer, and may be able todetermine the thicknesses of the top layer and the bottom layer, theconventional inspection system may be unable to determine which of thetop and bottom layers is the silicon layer and which is the silicondioxide layer.

In another example, during an automated silicon wafer thinning andpackaging process, the detailed structure of a multilayer wafer may beunknown. In this automated process, identifying a remaining siliconthickness may involve determining a thickness of: the lowest layer ofthe structure if the multilayer wafer resides on grinding tape, thesecond-lowest layer if the multilayer wafer resides on dicing tape, orthe third-lowest layer if the multilayer wafer resides on Die AttachmentFilm (DAF) tape attached to dicing tape. The exact thickness of theremaining silicon may be an important parameter for heat transfer inmodern semiconductor devices. While a conventional inspection system maybe able to determine that the multilayer wafer has multiple layers, andmay be able to determine the thicknesses of the layers, the conventionalinspection system may be unable to determine the compositions and orderof the layers. For example, a conventional inspection system may beunable to determine the thickness of a particular layer of a multilayerwafer, such as the layer that is intended to be the lowest layer of themultilayer wafer.

Therefore, conventional inspection systems may be unable to correctlyidentify differences in the compositions of different layers of amultilayer sample during an automated manufacturing process. Thisinability of conventional inspection systems may be result in undetectedproblems with the order of the layers in a multilayer sample, and thecorresponding orientation of the layers, such as undetected upside-downmultilayer samples, resulting in manufacturing defects during theautomated manufacturing process.

The subject matter claimed in this disclosure is not limited toembodiments that solve any disadvantages or that operate only inenvironments such as those described above. Rather, this background isonly provided to illustrate one example technology area where someembodiments described in this disclosure may be practiced.

SUMMARY

One example embodiment may include a method for inspecting a multilayersample. The method may include emitting, from a broadband light source,light over single mode optical fiber. The method may also includereceiving, at a beam splitter, the light and splitting, at the beamsplitter, the light into first and second portions. The method mayfurther include directing, from the beam splitter, the first portion ofthe light toward a multilayer sample positioned a first optical distancefrom the beam splitter. The method may also include directing, from thebeam splitter, the second portion of the light onto a reflectorpositioned a second optical distance from the beam splitter. The methodmay further include combining, at the beam splitter, the first portionof the light after being reflected from the multilayer sample and thesecond portion of the light after being reflected from the reflector.The method may also include directing, from the beam splitter, thecombined light over the optical fiber. The method may further includereceiving, at a computer-controlled system for analyzing Fabry-Perotfringes, the combined light over the optical fiber and spectrallyanalyzing the combined light using the system for analyzing Fabry-Perotfringes to determine a value of a total power impinging a slit of thesystem for analyzing Fabry-Perot fringes. The method may also includedetermining an optical path difference (OPD) between an optical path ofthe first portion of the light and an optical path of the second portionof the light. The method may further include recording an interferogramthat plots the value versus the OPD for the OPD. The method may alsoinclude performing the previous acts of the method one or moreadditional times after decreasing the first optical distance by movingthe multilayer sample closer to the beam splitter, or after increasingthe second optical distance by moving the reflector further away fromthe beam splitter, resulting in a different OPD. The method may furtherinclude using the interferogram for each of the different OPDs todetermine the thicknesses and order of the layers of the multilayersample.

In some embodiments, the method may further include receiving, at adirectional element, the light from the broadband light source over theoptical fiber and directing, from the directional element, the light tothe beam splitter over the optical fiber. In some embodiments, themethod may also include receiving, at the directional element, thecombined light from the beam splitter and directing, from thedirectional element, the combined light to using the system foranalyzing Fabry-Perot fringes. In some embodiments, the method mayfurther include positioning the multilayer sample so that the firstoptical distance is shorter than the second optical distance by morethan a coherence of the light emitted by the broadband light source. Insome embodiments, the spectrally analyzing of the combined light at thesystem for analyzing Fabry-Perot fringes may be performed over allchannels of the system for analyzing Fabry-Perot fringes. In someembodiments, the first optical distance may be decreased by an incrementsmaller than half of a wavelength of the first portion of the light. Insome embodiments, the performing of the previous acts of the method maycontinue until the OPD is less than an anticipated optical thickness ofthe multilayer sample. In some embodiments, the method may furtherinclude positioning the multilayer sample so that the first opticaldistance is longer than the second optical distance by more than acoherence of the light emitted by the broadband light source.

Another embodiment may include a system for inspecting a multilayersample. The system may include single mode optical fiber, a broadbandlight source, a beam splitter, a system for analyzing Fabry-Perotfringes, a motion stage, and a computer. The broadband light source maybe configured to emit light over the optical fiber. The beam splittermay be configured to receive the light from the broadband light sourceand split the light into first and second portions, direct the firstportion of the light toward a multilayer sample positioned a firstoptical distance from the beam splitter, direct the second portion ofthe light onto a reflector positioned a second optical distance from thebeam splitter, combine the first portion of the light after beingreflected from the multilayer sample and the second portion of the lightafter being reflected from the reflector, and direct the combined lightover the optical fiber. The system for analyzing Fabry-Perot fringes maybe configured to receive the combined light over the optical fiber andto spectrally analyze the combined light to measure a value of a totalpower impinging a slit of the system for analyzing Fabry-Perot fringes.The motion stage may be configured to decrease the first opticaldistance by moving the multilayer sample closer to the beam splitter orincrease the second optical distance by moving the reflector furtheraway from the beam splitter. The computer may be configured to controlthe system for analyzing Fabry-Perot fringes, determine an optical pathdifference (OPD) between an optical path of the first portion of thelight and an optical path of the second portion of the light, record aninterferogram that plots the value versus the OPD for each unique OPD,control the motion stage between measurements to change the OPD, and usethe interferograms to determine the thicknesses and order of the layersof the multilayer sample.

In some embodiments, the system further includes a directional elementconfigured to receive the light from the broadband light source over theoptical fiber, direct the light to the beam splitter over the opticalfiber, receive the combined light from the beam splitter, and direct thecombined light to the system for analyzing Fabry-Perot fringes. In someembodiments, the system also includes a point detector configured to beemployed when the system is operating in a Michelson interferometer modeand an optical switch configured to switch the combined light directedfrom directional element back and forth between the system for analyzingFabry-Perot fringes and the point detector. In some embodiments, thesystem for analyzing Fabry-Perot fringes is configured to spectrallyanalyze the combined light over all channels of the system for analyzingFabry-Perot fringes. In some embodiments, the computer may be configuredto control the motion stage between measurements to only change the OPDby an increment smaller than half of a wavelength of the first portionof the light. In some embodiments, the computer may be configured tocontrol the motion stage between measurements to change the OPD onlyuntil the OPD is less than an anticipated optical thickness of themultilayer sample.

It is to be understood that both the foregoing summary and the followingdetailed description are explanatory and are not restrictive of theinvention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

Example embodiments will be described and explained with additionalspecificity and detail through the use of the accompanying drawings inwhich:

FIG. 1 illustrates a first example system for inspecting a multilayersample;

FIG. 2 illustrates a second example system for inspecting a multilayersample;

FIG. 3 illustrates a third example system for inspecting a multilayersample;

FIG. 4 illustrates an example beam assembly that may be employed in thesystems of FIGS. 1-3;

FIG. 5A illustrates an example multilayer sample oriented upside down;

FIG. 5B illustrates the example multilayer sample of FIG. 5A orientedright side up;

FIGS. 6A and 6B illustrate simulated Michelson interferograms ofradiation that may be obtained by the systems of FIGS. 1-3 from the twoexample multilayer samples of FIGS. 5A and 5B, respectively;

FIGS. 6C and 6D illustrate simulated Fabry-Perot fringes interferogramsthat may be obtained from the two example multilayer samples of FIGS. 5Aand 5B, respectively; and

FIGS. 7A, 7B, and 7C illustrate a flowchart of an example method forinspecting a multilayer sample.

DESCRIPTION OF EMBODIMENTS

Unlike convention inspection systems, the embodiments disclosed hereinmay be able to correctly determine both the thicknesses and the order ofthe layers of a multilayer sample.

For example, during an automated manufacturing process, a multilayerwafer may have a silicon layer and a silicon dioxide layer, and themultilayer wafer may need to be oriented with the silicon layer on topto allow the silicon layer to be ground down during the automatedmanufacturing process to a specific thickness. The embodiments disclosedherein may be positioned above the multilayer wafer to inspect themultilayer wafer as it travels through the automated manufacturingprocess in order to measure the thickness of the top silicon layer toverify that the silicon layer is successfully ground down to thespecific thickness. In this example, the multilayer wafer mayinadvertently become turned upside down during the automatedmanufacturing process such that the silicon layer, which should be onthe top to be exposed for grinding down, ends up on the bottom. Theembodiments disclosed herein may be able to determine that themultilayer wafer has a top layer and a bottom layer, may be able todetermine the thicknesses of the top layer and the bottom layer, and maybe able to determine that the top layer is the silicon dioxide and thebottom layer is the silicon layer. Therefore, in this situation wherethe multilayer wafer inadvertently becomes turned upside down during theautomated manufacturing process, the embodiments disclosed herein may beable to determine that there is a problem, which may avoid the silicondioxide layer of the multilayer wafer being improperly ground down.

In another example, the use of systems that determine wafer thicknessusing spectral Fabry-Perot fringe analysis may measure only intensity ofreflected radiation and may lose information about the change of thephase of the radiation during the reflection process. In contrast,interferometers may retain this phase information. Thus, interferogramscollected by interferometers, such as Michelson interferometers, maycontain more information than the intensity spectra. Therefore,embodiments disclosed herein may be employed to utilize a system thatdetermines wafer thickness using spectral Fabry-Perot fringe analysisequipped with an additional reference mirror in order to collectinterferograms.

Therefore, the embodiments disclosed herein may be able to correctlyidentify differences in the compositions of different layers of amultilayer sample during an automated manufacturing process. Thisability of the embodiments disclosed herein may be result in thedetection of problems with the order of the layers in a multilayersample, and the corresponding orientation of the layers, such as anupside-down multilayer samples, thereby avoiding manufacturing defectsduring the automated manufacturing process.

Embodiments of the present disclosure will be explained with referenceto the accompanying drawings.

FIG. 1 illustrates a first example system 100 for inspecting amultilayer sample 500, arranged in accordance with at least someembodiments described in this disclosure. In general, the system 100 maybe configured to inspect the multilayer sample 500 to correctlydetermine the number of layers, the thickness of each layer, thecomposition of each layer, the order of the layers, and thecorresponding orientation of the layers. To perform the inspection, thesystem 100 may include single mode optical fibers 102-110, a broadbandlight source 112, a direction element 113, a beam splitter 114, areflector 116, a system 118 for analyzing Fabry-Perot fringes and acomputer 120.

In some embodiments, the broadband light source 112 may be configured toemit light over the optical fiber 102.

In some embodiments, the directional element 113 may be configured toreceive the light from the broadband light source 112 and direct thelight over the optical fiber 104 to the beam splitter 114.

In some embodiments, the beam splitter 114 may be configured to receivethe light from the directional element 113 and split the light intofirst and second portions. The beam splitter 114 may also be configuredto direct the first portion of the light over the optical fiber 106toward the multilayer sample 500 positioned a first optical distance D1from the beam splitter 114. The beam splitter 114 may further beconfigured to direct the second portion of the light over the opticalfiber 108 onto the reflector 116 positioned a second optical distance D2from the beam splitter 114. The beam splitter 114 may also be configuredto combine the first portion of the light after being reflected from themultilayer sample 500 and the second portion of the light after beingreflected from the reflector 116. The beam splitter 114 may further beconfigured direct the combined light over the optical fiber 104 backtoward the directional element 113.

In some embodiments, the directional element 113 may be configured toreceive the combined light from the beam splitter 114 and direct thecombined light over the optical fiber 110 toward the system 118 foranalyzing Fabry-Perot fringes.

In some embodiments, the system 118 for analyzing Fabry-Perot fringesmay be configured to receive the combined light over the optical fiber110. The system 118 for analyzing Fabry-Perot fringes may be furtherconfigured to spectrally analyze the combined light to measure a valueof a total power impinging a slit of the system 118 for analyzingFabry-Perot fringes. In some embodiments, the system 118 for analyzingFabry-Perot fringes may be configured to spectrally analyze the combinedlight over all channels of the system 118 for analyzing Fabry-Perotfringes. In some embodiments, the system 118 for analyzing Fabry-Perotfringes may include spectrometer. In some embodiments, the system 118for analyzing Fabry-Perot fringes may include a spectrometer combinedwith an etalon filter. An example of system 118 for analyzingFabry-Perot fringes that combines a spectrometer with an etalon filteris disclosed in U.S. patent application Ser. No. 15/410,328, filed Jan.19, 2017, which is incorporated herein by reference in its entirety.

In some embodiments, the system 100 may further include one or moremotion stages (not shown) configured to reposition the reflector 116and/or the multilayer sample 500 closer to, or further away from, thebeam splitter 114. In some embodiments, the one or more motion stagesmay be configured to decrease the first optical distance D1 by movingthe multilayer sample closer 500 to the beam splitter 114. In someembodiments, the one or more motion stages may be configured to increasethe second optical distance D2 by moving the reflector 116 further awayfrom the beam splitter 114. In some embodiments the one or more motionstages may be configured to both decrease the first optical distance D1by moving the multilayer sample 500 closer to the beam splitter 114 aswell as increase the second optical distance D2 by moving the reflector116 further away from the beam splitter 114. In some embodiments, thesystem 100 may allow measurement of the first optical distance D1 andmay be used to measure the topography, bow, and warp of the multilayersample 500.

In some embodiments, the computer 120 may be configured to control thesystem 118 for analyzing Fabry-Perot fringes, determine an optical pathdifference (OPD) between an optical path of the first portion of thelight and an optical path of the second portion of the light, record aninterferogram that plots the value versus the OPD for each unique OPD,control the motion stage between measurements to change the OPD, and usethe interferograms to determine the thicknesses and order of the layersof the multilayer sample 500. In some embodiments, the computer 120 maybe configured to control the one or more motion stages betweenmeasurements to only change the OPD by an increments smaller than halfof a wavelength of the first portion of the light. In some embodiments,the computer may be configured to control the motion stage betweenmeasurements to change the OPD by an increment equal to or larger thanhalf of a wavelength of the first portion of the light. In someembodiments, the computer 120 may be configured to control the one ormore motion stages between measurements to change the OPD only until theOPD is less than an anticipated optical thickness of the multilayersample 500.

In some embodiments, the computer 120 may include a processor and amemory. The processor may include, for example, a microprocessor,microcontroller, digital signal processor (DSP), application-specificintegrated circuit (ASIC), a Field-Programmable Gate Array (FPGA), orany other digital or analog circuitry configured to interpret and/or toexecute program instructions and/or to process data. In someembodiments, the processor may interpret and/or execute programinstructions and/or process data stored in the memory. The processor mayexecute instructions to perform operations with respect to the system118 for analyzing Fabry-Perot fringes and the one or more motion stagesin order to determine the thicknesses and order of the layers of themultilayer sample 500. The memory may include any suitablecomputer-readable media configured to retain program instructions and/ordata for a period of time. By way of example, and not limitation, suchcomputer-readable media may include tangible and/or non-transitorycomputer-readable storage media including Random Access Memory (RAM),Read-Only Memory (ROM), Electrically Erasable Programmable Read-OnlyMemory (EEPROM), Compact Disc Read-Only Memory (CD-ROM) or other opticaldisk storage, magnetic disk storage or other magnetic storage devices,flash memory devices (e.g., solid state memory devices), or any otherstorage medium which may be used to carry or store desired program codein the form of computer-executable instructions or data structures andwhich may be accessed by a general-purpose or special-purpose computer.Combinations of the above may also be included within the scope ofcomputer-readable media. Computer-executable instructions may include,for example, instructions and data that cause a general-purposecomputer, special-purpose computer, or special-purpose processing deviceto perform a certain function or group of functions.

The system 100 may be advantageously employed to inspect the multilayersample 500 to correctly determine the number of layers, the thickness ofeach layer, the composition of each layer, the order of the layers, andthe corresponding orientation of the layers. The system 100 may beadvantageously employed in a variety of environment, such as automatedmanufacturing process. For example, where the multilayer sample 500includes a silicon layer and a silicon dioxide layer, and where it isimportant that the silicon layer be on top, the system 100 may be ableto detect that the multilayer sample 500 is upside down as disclosed inFIG. 1, and thereby halt the automated manufacturing process until theorientation of the multilayer sample 500 is corrected in order toavoiding manufacturing defects during the automated manufacturingprocess.

FIG. 2 illustrates a second example system 200 for inspecting themultilayer sample 500, arranged in accordance with at least someembodiments described in this disclosure. The system 200 of FIG. 2 issimilar to the system 100 of FIG. 1, except that the system 200eliminates the directional element 113, the beam splitter 114, and theoptical fiber 104, and replaces these three components with a beamsplitter/directional element 115. The beam splitter/directional element115 of FIG. 2 combines the functionality of the directional element 113and the beam splitter 114 of FIG. 1. Otherwise, the system 200 of FIG. 2functions similarly to the system 100 of FIG. 1.

FIG. 3 illustrates a third example system 300 for inspecting themultilayer sample 500, arranged in accordance with at least someembodiments described in this disclosure. The system 300 of FIG. 3 issimilar to the system 100 of FIG. 1, except that the system 300 adds anoptical switch 122, optical fibers 124 and 126, and a point detector128.

In some embodiments, the optical switch 122 may be controlled by thecomputer 120 and may be configured to switch the combined light directedfrom directional element 113 over the optical fiber 110 back and forthbetween the system 118 for analyzing Fabry-Perot fringes, over theoptical fiber 124, and the point detector 128, over the optical fiber126. The point detector 128 may be configured to be employed when thesystem 300 is operating in a Michelson interferometer mode, and may becontrolled by the computer 120 in a similar manner as the system 118 foranalyzing Fabry-Perot fringes is controlled by the computer 120.

For example, one may observe multiple reflections of light insingle-layer and multilayer samples manifested in multiple interferencepeaks in Michelson interferograms. These reflections may be caused bymultiple light reflections from various sample interfaces. Light may bereflected back and forth several times inside the sample before thelight leaves the sample. These multiple scattering (reflection) pathsmay cause complications during Michelson interferogram analysis. Bycombining a Michelson interferometer with a Fabry-Perot interferometer,the analysis can be made easier. Fabry-Perot interferograms may help todetermine the thicknesses of various layers residing in the samplesfaster and more accurately, while Michelson interferograms may help todetermine their order (or sequence) relative to a probe head. Aninterferogram may contain more information about a sample since itcontains information about phase and magnitude of the reflectedelectromagnetic wave from the sample, while the reflected spectrumintensity may only contain information about amplitude of the reflectedradiation.

FIG. 4 illustrates an example beam assembly 400 that may be employed inthe systems 100, 200, and 300 of FIGS. 1-3, arranged in accordance withat least some embodiments described in this disclosure. In particular,the beam assembly 400 may be employed in place of the beam splitter 114and optical fibers 106 and 108 in the systems 100 and 300 of FIGS. 1 and3, and may be employed in place of the beam splitter functionality ofthe beam splitter/directional element 115 and the optical fibers 106 and108 of the system 200 of FIG. 2.

In some embodiments, the beam assembly 400 may include lenses 402 and404. The beam assembly 400 may also include a beam splitter 406 and areflector 408. The lens 402 may be configured to receiving the lightover the optical fiber 102 or 104 and collimate and direct the lighttoward the beam splitter 406. The beam splitter 406 may be configured tosplit the light from the lens 402 into first and second portions, directthe first portion of the light toward the lens 404, and direct thesecond portion of the light onto the reflector 408. The lens 404 may beconfigured to receive the first portion of the light from the beamsplitter 406, direct the first portion of the light toward themultilayer sample 500, and direct the first portion of the light afterbeing reflected from the multilayer sample 500 back toward the beamsplitter 406. Further, the reflector 408 may be configured to receivethe second portion of the light from the beam splitter 406 and reflectthe second portion of the light back toward the beam splitter 406. Thebeam splitter 406 may be further configured to combine the first portionof the light after being reflected from the multilayer sample 500 andthe second portion of the light after being reflected from the reflector408, and then direct the combined light toward the lens 402. Finally,the lens 402 may be configured to receive the combined light and directthe combined light over the optical fiber 102 or 104.

The beam assembly 400 may further include one or more motion stages (notshown) configured to reposition the reflector 408 and/or the multilayersample 500 closer to, or further away from, the beam splitter 406, inorder to adjust the optical distances D1 and D2, similarly to the one ormore motion stages discussed above in connection with FIG. 1.

FIG. 5A illustrates the example multilayer sample 500 oriented upsidedown and FIG. 5B illustrates the example multilayer sample 500 orientedright-side up. In some embodiments, the multilayer sample 500 may beinvolved in an automated manufacturing process where it is importantthat the silicon layer be on top. Therefore, in this scenario, themultilayer sample 500 of FIG. 5A is upside down and the multilayersample 500 of FIG. 5B is right-side up. The systems 100, 200, and 300disclosed herein may be employed to detect that the multilayer sample500 of FIG. 5A is upside down, and may thereby avoid manufacturingdefects during the automated manufacturing process by halting theautomated manufacturing process until the orientation of the multilayersample 500 is corrected as disclosed in FIG. 5B.

FIGS. 6A and 6B illustrate simulated Michelson interferograms 600 a and600 b of radiation that may be obtained by the systems 100, 200, and 300of FIGS. 1-3 from the two orientations of the multilayer sample 500 ofFIGS. 5A and 5B, respectively. FIGS. 6C and 6D illustrate simulatedFabry-Perot fringes interferograms 600 a and 600 b that may be obtainedfrom the two example multilayer samples of FIGS. 5A and 5B,respectively. In contrast to the simulated Fabry-Perot fringesinterferograms 600 c and 600 d of FIGS. 6C and 6D which appearidentical, the simulated Michelson interferograms 600 a and 600 b appeardifferent. As disclosed in the simulated Michelson interferograms 600 aand 600 b, the systems 100, 200, and 300 of FIGS. 1-3 may be able todistinguish between the silicon layer being on the bottom (as indicatedin the simulated Michelson interferogram 600 a) and the silicon layerbeing on the bottom (as indicated in the simulated Michelsoninterferogram 600 b). Additionally, due to multiple reflections in thesimulated Michelson interferograms 600 a and 600 b, the simulatedFabry-Perot interferograms 600 c and 600 d may be employed to helpdefine the number of layers in the multilayer sample 500, while thesimulated Michelson interferograms 600 a and 600 b may be employed tohelp define the order of the layers relative to the system systems 100,200, and 300 of FIGS. 1-3. Thus the thickness and order of the layers ofthe multilayer sample 500 of FIGS. 5A and 5B may be determined using thesystems 100, 200, and 300 of FIGS. 1-3.

FIGS. 7A, 7B, and 7C illustrate a flowchart of an example method 700 forinspecting a multilayer sample, arranged in accordance with at leastsome embodiments described in this disclosure. The method 700 may beimplemented, in some embodiments, by a system, such as any of thesystems 100, 200, and 300 of FIGS. 1, 2, and 3, respectively. Althoughillustrated as discrete blocks, various blocks may be divided intoadditional blocks, combined into fewer blocks, or eliminated, dependingon the desired implementation.

With reference to FIG. 7A, block 702 may include emitting, from abroadband light source, light over single mode optical fiber. Forexample, the broadband light source 112 of FIG. 2 may emit, at block702, light over the single mode optical fiber 102.

Block 704 may include receiving, at a beam splitter, the light andsplitting, at the beam splitter, the light into first and secondportions. For example, the beam splitter/directing element 115 of FIG. 2may receive, at block 704, the light over the single mode optical fiber102 and may split the light into first and second portions.

The block 706 may include directing, from the beam splitter, the firstportion of the light toward a multilayer sample positioned a firstoptical distance from the beam splitter. For example, the beamsplitter/directing element 115 of FIG. 2 may direct, at block 706, thefirst portion of the light over the optical fiber 106 toward themultilayer sample 500 positioned a first optical distance D1 from thebeam splitter/directing element 115.

The block 708 may include directing, from the beam splitter, the secondportion of the light onto a reflector positioned a second opticaldistance from the beam splitter. For example, the beamsplitter/directing element 115 of FIG. 2 may direct, at block 708, thesecond portion of the light over the optical fiber 108 onto thereflector 116 positioned a second optical distance D2 from the beamsplitter/directing element 115.

The block 710 may include combining, at the beam splitter, the firstportion of the light after being reflected from the multilayer sampleand the second portion of the light after being reflected from thereflector. For example, the beam splitter/directing element 115 of FIG.2 may combine, at block 710, the first portion of the light after beingreflected from the multilayer sample 500 and the second portion of thelight after being reflected from the reflector 116.

The block 712 may include directing, from the beam splitter, thecombined light over the optical fiber. For example, the beamsplitter/directing element 115 of FIG. 2 may direct, at block 712, thecombined light over the optical fiber 110.

With reference to FIG. 7B, the block 714 may include receiving, at acomputer-controlled system for analyzing Fabry-Perot fringes, thecombined light over the optical fiber and spectrally analyzing thecombined light at using the system for analyzing Fabry-Perot fringes todetermine a value of a total power impinging a slit of the system foranalyzing Fabry-Perot fringes. For example, the system 118 for analyzingFabry-Perot fringes of FIG. 2 may receive, at block 714, the combinedlight over the optical fiber 110 and spectrally analyze the combinedlight to determine a value of a total power impinging a slit of thesystem 110 for analyzing Fabry-Perot fringes. In some embodiments, thespectrally analysis may be performed over all channels of the system foranalyzing Fabry-Perot fringes.

The block 716 may include determining an optical path difference (OPD)between an optical path of the first portion of the light and an opticalpath of the second portion of the light. For example, the computer 120of FIG. 2 may determine, at block 716, an optical path difference (OPD)between an optical path of the first portion of the light and an opticalpath of the second portion of the light.

The block 718 may include recording an interferogram that plots thevalue versus the OPD for the OPD. For example, the computer 120 of FIG.2 may record, at block 716, an interferogram that plots the value versusthe OPD for the OPD.

The decision block 720 may include determining whether the OPD is lessthan an anticipated optical thickness of the multilayer sample. If so(Yes at the decision block 720), the method may conclude with block 726.If not (No at decision block 720), the method may continue with eitherblock 722 or block 724 and then return to block 702.

With reference to FIG. 7C, the block 722 may include decreasing thefirst optical distance by moving the multilayer sample closer to thebeam splitter resulting in a different OPD. For example, the computer120 of FIG. 2 may decrease, at block 722, the first optical distance D1moving the multilayer sample 500, using a motion stage for example,closer to the beam splitter/directing element 115 resulting in adifferent OPD. In some embodiments, the first optical distance may bedecreased at block 722 by an increment smaller than half of a wavelengthof the first portion of the light.

The block 724 may include increasing the second optical distance bymoving the reflector further away from the beam splitter resulting in adifferent OPD. For example, the computer 120 of FIG. 2 may increase, atblock 724, the second optical distance D2 by moving the reflector 116,using a motion stage for example, further away from the beamsplitter/directing element 115 resulting in a different OPD. In someembodiments, the second optical distance may be increased at block 724by an increment smaller than half of a wavelength of the first portionof the light.

After a different OPD has been achieved in block 722 or block 724, themethod may return to block 702 and repeat blocks 702-720 with thedifferent OPD. This process may be iteratively repeated until the OPD isless than an anticipated optical thickness of the multilayer sample, atwhich point the method may continue to block 726.

With reference to FIG. 7A, the block 726 may include using the recordedinterferogram for each of the different OPDs to determine thethicknesses and order of the layers of the multilayer sample. Forexample, the computer 120 of FIG. 2 may use, at block 7264, the recordedinterferogram for each of the different OPDs to determine thethicknesses and order of the layers of the multilayer sample 500. Inthis example, the computer 120 of FIG. 2 may determine that the toplayer of the multilayer sample 500 is the silicon dioxide layer with athickness of 10 microns (see FIG. 5A), and the bottom layer of themultilayer sample 500 is the silicon layer with a thickness of 120microns (see FIG. 5A).

One skilled in the art will appreciate that, for this and other methodsdisclosed in this disclosure, the blocks of the methods may beimplemented in differing order. Furthermore, the blocks are onlyprovided as examples, and some of the blocks may be optional, combinedinto fewer blocks, or expanded into additional blocks.

For example, in some embodiments, an additional block may be included inthe method 700 that includes positioning the multilayer sample so thatthe first optical distance is shorter than the second optical distanceby more than a coherence of the light emitted by the broadband lightsource. For example, the multilayer sample 500 of FIG. 2 may bepositioned prior to block 702 so that the first optical distance D1 isshorter than the second optical distance D2 by more than a coherence ofthe light emitted by the broadband light source 112.

Further, in some embodiments, an additional block may be included in themethod 700 that includes positioning the multilayer sample so that thefirst optical distance is longer than the second optical distance bymore than a coherence of the light emitted by the broadband lightsource. For example, the multilayer sample 500 of FIG. 2 may bepositioned prior to block 702 so that the first optical distance D1 islonger than the second optical distance D2 by more than a coherence ofthe light emitted by the broadband light source 112.

Terms used in this disclosure and especially in the appended claims(e.g., bodies of the appended claims) are generally intended as “open”terms (e.g., the term “including” should be interpreted as “including,but not limited to,” the term “having” should be interpreted as “havingat least,” the term “includes” should be interpreted as “includes, butis not limited to,” etc.).

Additionally, if a specific number of an introduced claim recitation isintended, such an intent will be explicitly recited in the claim, and inthe absence of such recitation no such intent is present. For example,as an aid to understanding, the following appended claims may containusage of the introductory phrases “at least one” and “one or more” tointroduce claim recitations. However, the use of such phrases should notbe construed to imply that the introduction of a claim recitation by theindefinite articles “a” or “an” limits any particular claim containingsuch introduced claim recitation to embodiments containing only one suchrecitation, even when the same claim includes the introductory phrases“one or more” or “at least one” and indefinite articles such as “a” or“an” (e.g., “a” and/or “an” should be interpreted to mean “at least one”or “one or more”); the same holds true for the use of definite articlesused to introduce claim recitations.

In addition, even if a specific number of an introduced claim recitationis explicitly recited, those skilled in the art will recognize that suchrecitation should be interpreted to mean at least the recited number(e.g., the bare recitation of “two recitations,” without othermodifiers, means at least two recitations, or two or more recitations).Furthermore, in those instances where a convention analogous to “atleast one of A, B, and C, etc.” or “one or more of A, B, and C, etc.” isused, in general such a construction is intended to include A alone, Balone, C alone, A and B together, A and C together, B and C together, orA, B, and C together, etc. For example, the use of the term “and/or” isintended to be construed in this manner.

Further, any disjunctive word or phrase presenting two or morealternative terms, whether in the description of embodiments, claims, ordrawings, should be understood to contemplate the possibilities ofincluding one of the terms, either of the terms, or both terms. Forexample, the phrase “A or B” should be understood to include thepossibilities of “A” or “B” or “A and B.”

All examples and conditional language recited in this disclosure areintended for pedagogical objects to aid the reader in understanding theinvention and the concepts contributed by the inventor to furthering theart, and are to be construed as being without limitation to suchspecifically recited examples and conditions. Although embodiments ofthe present disclosure have been described in detail, it should beunderstood that various changes, substitutions, and alterations could bemade hereto without departing from the spirit and scope of the presentdisclosure.

1. A method for inspecting a multilayer sample, the method comprising:(b) emitting light from a broadband light source optical; (c) receiving,at a beam splitter, the light and splitting, at the beam splitter, thelight into first and second portions; (d) directing, from the beamsplitter, the first portion of the light toward a multilayer samplepositioned a first optical distance from the beam splitter; (e)directing, from the beam splitter, the second portion of the light ontoa reflector positioned a second optical distance from the beam splitter;(f) combining, at the beam splitter, the first portion of the lightafter being reflected from the multilayer sample and the second portionof the light after being reflected from the reflector; (g) directing,from the beam splitter, the combined light over a single mode opticalfiber toward a system for analyzing Fabry-Perot fringes; (h) receiving,at a computer-controlled spectrograph included in the system foranalyzing Fabry-Perot fringes, the combined light and spectrallyanalyzing the combined light using the computer-controlled spectrographto determine a value of a total power impinging a slit of the system foranalyzing Fabry-Perot fringes; (i) determining an optical pathdifference (OPD) between an optical path of the first portion of thelight and an optical path of the second portion of the light; (j)recording an interferogram that plots the value versus the OPD for theOPD; (k) performing (b)-(j) one or more additional times afterdecreasing the first optical distance by moving the multilayer samplecloser to the beam splitter resulting in a different OPD; and (l) usingthe interferogram for each of the different OPDs to determine thethicknesses and order of the layers of the multilayer sample.
 2. Themethod of claim 1, further comprising: (b1) receiving, at a directionalelement, the light from the broadband light source over the opticalfiber and directing, from the directional element, the light to the beamsplitter over the optical fiber; and (b2) the method further comprisesreceiving, at the directional element, the combined light from the beamsplitter and directing, from the directional element, the combined lightto using the system for analyzing Fabry-Perot fringes.
 3. The method ofclaim 1, further comprising: (a) positioning the multilayer sample sothat the first optical distance is shorter than the second opticaldistance by more than a coherence of the light emitted by the broadbandlight source at (b).
 4. The method of claim 1, wherein the spectrallyanalyzing of the combined light at the system for analyzing Fabry-Perotfringes at (h) is performed over all channels of the system foranalyzing Fabry-Perot fringes.
 5. The method of claim 1, wherein thefirst optical distance is decreased at (k) by an increment smaller thanhalf of a wavelength of the first portion of the light.
 6. The method ofclaim 5, wherein (b)-(j) are performed at (k) until the OPD is less thanan anticipated optical thickness of the multilayer sample.
 7. The methodof claim 1, wherein the system for analyzing Fabry-Perot fringesincludes a computer-controlled etalon filter configured to filter thecombined light and direct the filtered combined light toward thecomputer-controlled spectrograph via a single-mode optical fiber of thesystem for analyzing Fabry-Perot fringes.
 8. A method for inspecting amultilayer sample, the method comprising: (b) emitting light from abroadband light source; (c) receiving, at a beam splitter, the light andsplitting, at the beam splitter, the light into first and secondportions; (d) directing, from the beam splitter, the first portion ofthe light toward a multilayer sample positioned a first optical distancefrom the beam splitter; (e) directing, from the beam splitter, thesecond portion of the light onto a reflector positioned a second opticaldistance from the beam splitter; (f) combining, at the beam splitter,the first portion of the light after being reflected from the multilayersample and the second portion of the light after being reflected fromthe reflector; (g) directing, from the beam splitter, the combined lightover a first single-mode optical fiber toward a system for analyzingFabry-Perot fringes; (h) receiving, at the system for analyzingFabry-Perot fringes, the combined light, directing the combined lightover a second single-mode optical fiber, receiving at acomputer-controlled spectrograph included in the system for analyzingFabry-Perot fringes, the combined light over the second single-modeoptical fiber, and spectrally analyzing the combined light using thecomputer-controlled spectrograph to determine a value of a total powerimpinging a slit of the system for analyzing Fabry-Perot fringes; (i)determining an optical path difference (OPD) between an optical path ofthe first portion of the light and an optical path of the second portionof the light; (j) recording an interferogram that plots the value versusthe OPD for the OPD; (k) performing (a)-(j) one or more additional timesafter increasing the second optical distance by moving the reflectorfurther away from the beam splitter resulting in a different OPD; and(l) using the interferogram for each of the different OPDs to determinethe thicknesses and order of the layers of the multilayer sample.
 9. Themethod of claim 8, further comprising: (b1) receiving, at a directionalelement, the light from the broadband light source and directing, fromthe directional element, the light to the beam splitter; and (b2) themethod further comprises receiving, at the directional element, thecombined light from the beam splitter and directing, from thedirectional element, the combined light to the system for analyzingFabry-Perot fringes.
 10. The method of claim 8, further comprising: (a)positioning the multilayer sample so that the first optical distance islonger than the second optical distance by more than a coherence of thelight emitted by the broadband light source at (b).
 11. The method ofclaim 8, wherein the spectrally analyzing of the combined light at thesystem for analyzing Fabry-Perot fringes at (h) is performed over allchannels of the system for analyzing Fabry-Perot fringes.
 12. The methodof claim 8, wherein the second optical distance is increased at (k) byan increment smaller than half of a wavelength of the first portion ofthe light.
 13. The method of claim 12, wherein (a)-(j) are performed at(k) until the OPD is less than an anticipated optical thickness of themultilayer sample.
 14. The method of claim 8, wherein the system foranalyzing Fabry-Perot fringes includes a computer-controlled etalonfilter configured to filter the combined light and direct the filteredcombined light toward the computer-controlled spectrograph over thesecond single-mode optical fiber.
 15. A system for inspecting amultilayer sample, the system comprising: a broadband light sourceconfigured to emit light; a beam splitter configured to receive thelight from the broadband light source and split the light into first andsecond portions, direct the first portion of the light toward amultilayer sample positioned a first optical distance from the beamsplitter, direct the second portion of the light onto a reflectorpositioned a second optical distance from the beam splitter, combine thefirst portion of the light after being reflected from the multilayersample and the second portion of the light after being reflected fromthe reflector, and direct the combined light toward a system foranalyzing Fabry-Perot fringes; the system for analyzing Fabry-Perotfringes configured to receive the combined light, direct the combinedlight over a single-mode optical fiber of the system for analyzingFabry-Perot fringes, receive, at a computer-controlled spectrographincluded in the system for analyzing Fabry-Perot fringes, the combinedlight over the single-mode optical fiber, and spectrally analyze thecombined light, using the computer-controlled spectrograph, to measure avalue of a total power impinging a slit of the system for analyzingFabry-Perot fringes; a motion stage configured to decrease the firstoptical distance by moving the multilayer sample closer to the beamsplitter or increase the second optical distance by moving the reflectorfurther away from the beam splitter; and a computer configured tocontrol the system for analyzing Fabry-Perot fringes, determine anoptical path difference (OPD) between an optical path of the firstportion of the light and an optical path of the second portion of thelight, record an interferogram that plots the value versus the OPD foreach unique OPD, control the motion stage between measurements to changethe OPD, and use the interferograms to determine the thicknesses andorder of the layers of the multilayer sample.
 16. The system of claim15, further comprising: a directional element configured to receive thelight from the broadband light source, direct the light to the beamsplitter, receive the combined light from the beam splitter, and directthe combined light to the system for analyzing Fabry-Perot fringes. 17.The system of claim 16, further comprising: a point detector configuredto be employed when the system is operating in a Michelsoninterferometer mode; and an optical switch configured to switch thecombined light directed from directional element back and forth betweenthe system for analyzing Fabry-Perot fringes and the point detector. 18.The system of claim 15, wherein the system for analyzing Fabry-Perotfringes is configured to spectrally analyze the combined light over allchannels of the system for analyzing Fabry-Perot fringes.
 19. The systemof claim 15, wherein the computer is configured to control the motionstage between measurements to only change the OPD by an incrementsmaller than half of a wavelength of the first portion of the light. 20.The system of claim 19, wherein computer is configured to control themotion stage between measurements to change the OPD only until the OPDis less than an anticipated optical thickness of the multilayer sample.